{% load widget_tweaks %}
{% for field in form %}
  <div class="form-group">
    {{ field.label_tag }}
    {% if form.is_bound %}
      {% if field.errors %}
        {% render_field field class="form-control is-invalid" %}
        {% for error in field.errors %}
          <div class="invalid-feedback">
            {{ error }}
          </div>
        {% endfor %}
      {% else %}
        {% render_field field class="form-control is-valid" %}
      {% endif %}
    {% else %}
      {% render_field field class="form-control" %}
    {% endif %}
    {% if field.help_text %}
      <small class="form-text text-muted">
        {{ field.help_text|safe }}  <!-- 新的代码 -->
      </small>
    {% endif %}
  </div>
{% endfor %}